1. Field
The present disclosure is directed to a method and apparatus for controlling charging and/or discharging of a plurality of batteries within a user device. More particularly, the present disclosure is directed to controlling individual charging and/or controlling simultaneous discharging of the plurality of batteries based on a temperature of one or more of the plurality of batteries.
2. Introduction
Presently, customers carry user devices so as to be able to use them to communicate. The scenarios of use of such user devices are varied, and their use in extreme hot or extreme cold weather exposure imposes limitations on an ability of a battery to power the user device.
In particular, if a battery of the user device is allowed to cool down below a certain temperature, internal chemistry (reaction rate) of the battery becomes sluggish, resulting in low energy delivery and/or high charge transfer impedance. Such battery issues become more pronounced in an older aged battery. For example, a lithium-ion (Li-ion) battery can provide approximately 10-15% power at 0.2 degrees centigrade when new. However, as the Li-ion battery ages, the power that can be produced reduces.
An amount of power a battery can produce eventually reduces enough to the point at which the battery cannot generate sufficient power to power up and run the user device. Such a reduction is particularly a problem when the battery becomes too cold and the user device is being used for an emergency phone call. Such a reduced state can even occur when the battery is in a fully charged state and becomes too cold. In other scenarios, increased battery impedance at cold temperatures, combined with high peak currents and a low state of charge, induces a voltage dip below a threshold voltage. This voltage dip causes power management integrated circuitry to shut down the user device when this voltage dip is detected. Furthermore, charging a battery below a certain temperature is deleterious to the health of the battery, leading to such problems as Li-plating that causes a drop in battery performance and in extreme cases leads to short-circuits.
Additionally, charging a battery generates heat. Too much heat in any one battery or portion of a battery pack, or cell, prematurely ages the battery and/or cell and decreases its expected life. Moreover, charging a battery in a user device that is already hot will introduce even more heat within the user device, potentially pushing electric components within the user device past a safe operating temperature.
Moreover, uniform self-heating under cold temperatures during charging and/or discharging of a battery is critical for battery health. Uniform self-heating does not occur for aged batteries, depending on battery usage history. In particular, aged batteries experience non-uniform current distribution among electrode layers that leads to non-uniform self-heating.